22 Development of the Fern Leaf 
segments a and b, b obviously will now be at the left side of the 
base of this rachis if the right one, at the right side. 
If, now, of the two segments at the apex of this rachis, which 
may be designated as c and d, one (c) becomes transformed into 
a stalk with two segments at apex, in the same manner as the 
original simple leaf or segment and as @ was transformed, and 
the other (d) remains undivided, the latter stalk will constitute 
a second section of rachis which will separate the latter pair of 
segments from d, while the first section of rachis will still separate 
d from a. If d were the left one of the segments c and d, d will 
now be at the left side of the base of this second section of rachis; 
if the right one, at the right side. D and b may, therefore, be 
either on the same side of the rachis composed of the two sections 
or on opposite sides. If on opposite sides, they will be alternate, 
since they will be separated by the length of a vein. This vein 
may, however, be so short as to be imperceptible to the naked 
eye, in which case they will appear opposite. 
If, instead of the segments subdividing in the above-described 
order, the original simple leaf-blade or segment becomes trans- 
formed into a stalk with two segments at apex, in the manner 
above described (z.e., by subdividing into segments and becoming 
attenuate below these segments), and each of the latter segments 
becomes transformed likewise into a stalk with two segments at 
apex, a dichotomous rachis with two segments at each end of its 
fork will result; for this reason. The starting-points of the two 
segments formed by the subdividing of the original simple leaf- 
blade or segment will also be the apex of the stalk composed of 
the lower part of the latter; hence, when the lower parts of these 
segments shall have become stalks, the starting-points of the latter 
